Wrist

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wrist joint
Hand parts.jpg
A human hand with wrist labeled at left.
Latin articulatio radiocarpea
Gray's p.327
MeSH Wrist+joint

In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;[1][2] (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus;[2] and (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints.[3][4] This region also includes the carpal tunnel, the anatomical snuff box, the flexor retinaculum, and the extensor retinaculum.

As a consequence of these various definitions, fractures to the carpal bones are referred to as carpal fractures, while fractures such as distal radius fracture are considered fractures to the wrist. [5]

Structure[edit]

Posterior and anterior aspects of right human wrist
Ligaments of wrist. Posterior and anterior views

Articulations[edit]

The radiocarpal, intercarpal, midcarpal, carpometacarpal, and intermetacarpal joints often intercommunicate through a common synovial cavity. [6]

Micro-radiography of 8 weeks human embryo hand

Extrinsic hand[edit]

The distal radioulnar joint is a pivot joint located between the bones of the forearm, the radius and ulna. Formed by the head of ulna and the ulnar notch of radius, this joint is separated from the radiocarpal joint by an articular disk lying between the radius and the styloid process of ulna. The capsule of the joint is lax and extends from the inferior sacciform recess to the ulnar shaft. Together with the proximal radioulnar joint, the distal radioulnar joint permits pronation and supination. [7]

The radiocarpal joint or wrist joint is an ellipsoid joint formed by the radius and the articular disc proximally and the proximal row of carpal bones distally. The carpal bones on the ulnar side only make intermittent contact with the proximal side — the triquetrum only makes contact during ulnar abduction. The capsule, lax and un-branched, is thin on the dorsal side and can contain synovial folds. The capsule is continuous with the midcarpal joint and strengthened by numerous ligaments, including the palmar and dorsal radiocarpal ligaments, and the ulnar and radial collateral ligaments. [8]

The parts forming the radiocarpal joint are the lower end of the radius and under surface of the articular disk above; and the scaphoid, lunate, and triquetral bones below. The articular surface of the radius and the under surface of the articular disk form together a transversely elliptical concave surface, the receiving cavity. The superior articular surfaces of the scaphoid, lunate, and triquetrum form a smooth convex surface, the condyle, which is received into the concavity.

Carpal bones of the hand:

In the hand proper a total of 13 bones form part of the wrist: eight carpal bonesscaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate, and hamate— and five metacarpal bones—the first, second, third, fourth, and fifth metacarpal bones.[9]

The midcarpal joint is the S-shaped joint space separating the proximal and distal rows of carpal bones. The intercarpal joints, between the bones of each row, are strengthened by the radiate carpal and pisohamate ligaments and the palmar, interosseous, and dorsal intercarpal ligaments. Some degree of mobility is possible between the bones of the proximal row while the bones of the distal row are connected to each other and to the metacarpal bones —at the carpometacarpal joints— by strong ligaments —the pisometacarpal and palmar and dorsal carpometacarpal ligament— that makes a functional entity of these bones. Additionally, the joints between the bases of the metacarpal bones —the intermetacarpal articulations— are strengthened by dorsal, interosseous, and palmar intermetacarpal ligaments. [8]

Function[edit]

Movements and muscles[edit]

The extrinsic hand muscles are located in the forearm where their bellies form the proximal fleshy roundness. When contracted, most of the tendons of these muscles are prevented from standing up like taut bowstrings around the wrist by passing under the flexor retinaculum on the palmar side and the extensor retinaculum on the dorsal side. On the palmar side the carpal bones form the carpal tunnel through which some of the flexor tendons pass in tendon sheaths that enable them to slide back and forth through the narrow passageway (see carpal tunnel syndrome). [10]

Starting from the mid-position of the hand, the movements permitted in the wrist proper are (muscles in order of importance):[11][12]

However, movements at the wrist can not be properly described without including movements in the distal radioulnar joint in which the rotary actions of supination and pronation occur and this joint is therefore normally regarded as part of the wrist. [13]

History[edit]

Etymology[edit]

The English word "wrist" is etymologically derived from the ancient German word wristiz from which are derived modern German rist ("instep", "wrist") and modern Swedish vrist ("instep", "ankle"). The base writh- and its variants are associated with Old English words "wreath", "wrest", and "writhe". The wr- sound of this base seems originally to have been symbolic of the action of twisting. [14]

See also[edit]

Additional Images[edit]

Notes[edit]

  1. ^ Behnke 2006, p. 76. "The wrist contains eight bones, roughly aligned in two rows, known as the carpal bones."
  2. ^ a b Moore 2006, p. 485. "The wrist (carpus), the proximal segment of the hand, is a complex of eight carpal bones. The carpus articulates proximally with the forearm at the wrist joint and distally with the five metacarpals. The joints formed by the carpus include the wrist (radiocarpal joint), intercarpal, carpometacarpal and intermetacarpal joints. Augmenting movement at the wrist joint, the rows of carpals glide on each other [...] "
  3. ^ Behnke 2006, p. 77. "With the large number of bones composing the wrist (ulna, radius, eight carpas, and five metacarpals), it makes sense that there are many, many joints that make up the structure known as the wrist."
  4. ^ Baratz 1999, p. 391. "The wrist joint is composed of not only the radiocarpal and distal radioulnar joints but also the intercarpal articulations."
  5. ^ "Fractures, Wrist". eMedicine, Medscape. Retrieved August 2009. "Fractures of the distal radius, ulna, or both account for approximately three quarters of bony injuries of the wrist." 
  6. ^ Isenberg 2004, p. 87
  7. ^ Platzer 2004, p. 122
  8. ^ a b Platzer 2004, p. 130
  9. ^ Platzer 2004, pp. 126–129
  10. ^ Saladin, 2003, pp. 361, 365
  11. ^ Platzer 2004, p. 132
  12. ^ Platzer 2004, p. 172
  13. ^ Kingston 2000, pp. 126–127
  14. ^ "Hand Etymology". American Society for Surgery of the Hand. Retrieved August 2009. 

References[edit]

External links[edit]